Threatened moss carder bumblebees in Britain have suffered a 25% drop in genetic diversity over the past century, driven by habitat loss, wetland drainage, and pesticide use, according to a recent study examining museum specimens. In England and Wales, inbreeding has nearly tripled as populations shrink and isolate.
A study published in Molecular Biology and Evolution details how moss carder bumblebees are rapidly losing genetic diversity across Britain. Researchers examined DNA from more than 100 museum specimens stored at the Natural History Museum and other institutions, including the Oxford University Museum of Natural History, Tullie Museum & Art Gallery, World Museum, and National Museums Scotland. These specimens, collected between 1890 and 2019, provided the necessary historical baseline to track long-term population shifts.
Museum DNA Reveals Century-Long Decline in Genetic Health
Across Britain, overall genetic diversity in moss carder bumblebees has declined steadily since the late 19th century, falling by around a quarter over the past 100 years. The situation is particularly acute in England and Wales, where populations have experienced an almost three-fold increase in the proportion of the genome affected by inbreeding. According to the research team, this surge highlights the shrinking and isolating nature of remaining colonies as wetland drainage, pesticide use, and the loss of flower-rich meadows, marshes, and heathland take their toll. The researchers described the rate of genetic diversity loss as unexpectedly high, emphasising the speed at which these pollinators are being affected.
This research confirms what we’ve suspected for some time – the declining population of the moss carder bee is eroding its genetic diversity. As the genome is like a toolkit, containing all the different ways a species can adapt, these bees now have fewer tools available to them in their response to climate change, pollution and habitat degradation.
Dr Victoria Mullin, Assistant Professor at Trinity College Dublin and co-author of the study
The study highlights that moss carder bumblebees once inhabited vast areas of the UK, pollinating numerous plant species within heathlands, marshes, and flower-rich meadows. As those environments disappeared, the species retreated into strongholds along the country’s coasts and islands.
This kind of research has been enabled by initiatives like the Darwin Tree of Life, which seeks to sequence the genomes of over 70,000 UK species. This was particularly beneficial for the researchers studying the moss carder bumblebee, a species that is famously difficult for even trained experts to identify. By utilizing this genome as a reference, the team discovered that 29 museum specimens previously labeled as moss carder bumblebees were actually close relatives.
To understand these changes, museum collections are key. We have around 30 million insects at the Natural History Museum, and millions more in other UK museums, which provide the scale needed to answer some of the most important questions humanity faces today.
Professor Ian Barnes, Merit Researcher at the Natural History Museum and co-author of the study
Contrasting Fortunes in the Scottish Highlands and New Conservation Funding
Although bumblebee populations in the Scottish Highlands also appear to be dropping, they seem to be less affected by the fragmentation of their habitat. Researchers suggest that Scottish habitats still retain the connectivity that allows bees from different populations to mix.
To help address the species’ struggles, a three-year scheme led by the Bumblebee Conservation Trust alongside the University of Cambridge is targeting the recovery of the moss carder species. Backed by more than £530,000 in funding provided by Natural England’s Species Recovery Programme as part of a total £907,000 project, the initiative focuses on landscapes across Cornwall’s coastal grasslands, dunes, and heathland, alongside grazing marshes and sea walls in Kent and the upland fringe landscape of the North Pennines. Throughout the project, the trust will collaborate with landowners to test small-scale habitat interventions to determine which are most effective while improving their knowledge of the species’ needs and behaviour. Moss carder bumblebees are distinctive with a velvety covering of ginger-yellow hairs across its body and no black hairs, and habitat loss and fragmentation are likely to have a bigger impact on them than many other species as they typically forage closer to their nests than most other bumblebees.
This is a hugely exciting and ambitious three-year project that gives us a real opportunity to turn the tide for one of the UK’s rarest bumblebees.
Amy Plowman, head of conservation and science at the Bumblebee Conservation Trust
Tylan Berry, Natural England’s species and nature recovery networks senior officer, stated that the Species Recovery Programme was helping take practical action to halt species decline and support nature recovery across England, noting that the moss carder was one of England’s most threatened pollinators. Berry added that projects like this demonstrate how targeted investment can support practical conservation action on the ground.
Researchers involved in the genomic study suggest that introducing Scottish individuals to English and Welsh populations could eventually help to restore their genetic diversity as part of carefully planned conservation projects, provided this would first require tackling the root causes of the bumblebee’s decline.
